Explanation

Hazrat Ummay Salma (RA) is the wife known by the title Umm-ul-Masakeen. Hazrat Ummay Habiba (RA) is another prominent wife but not specifically titled this way. Hazrat Zainab bint e Khuzaiymah (RA) is a different person and does not hold this specific title. Hazrat Zainab Bint-t-Jahsh is a different individual.